Over voltage arrester

ABSTRACT

A voltage arrester having a tubular insulating member with a pair of electrodes disposed at opposite ends of the tubular member and facing inwardly thereof. The electrodes are frustumshaped and have surfaces facing each other and spaced apart adjacent the center of the tubular insulating member. A relatively large contact block is placed in good thermal conductive relationship with each of the respective electrodes. The contact blocks are formed of a good thermal conducting material and are slidably disposed in a housing which contains the voltage arrester. The housing is tubular shaped, and a bias spring urges one of the contact blocks together with the insulating member and the associated electrodes toward the other contact block. The other contact block is held in fixed position by a fusible material which when melted allows the entire assembly to slide within the housing. A further electrode is formed as a cylindrical member disposed within the housing and electrically coupled to one of the contact blocks and having a surface positioned to and spaced from the other contact block. When the fusible material is melted, the other contact block is moved into engagement with the surface of the further electrode.

United States Patent Bahr et al. [451 Mar. 21, 1972 [54] OVER VOLTAGE ARRESTER Primary Examiner-Bemard A. Gilheany Assistant Examiner-F. E. Bell [72] Inventors. Alex Bahr, Gerhard Lange, both of Berlin, Atwmey Hm Sherman Memni, Gross & Simpson Germany [73] Assignee: Siemens Aktiengesellschaft, Berlin and [57] ABSTRACT Munich Germany A voltage arrester having a tubular insulating member with a [22] Filed: May 4, 1970 pair of electrodes disposed at opposite ends of the tubular member and facing inwardly thereof. The electrodes are Appl 34300 frustum-shaped and have surfaces facing each other and 4 spaced apart adjacent the center of the tubular insulating [30] Foreign Application Prlorlty Data member. A relatively large contact block is placed in good thermal conductive relationship with each of the respective May 1969 Germany 19 22 823") electrodes. The contact blocks, are formed of a good thermal conducting material and are slidably disposed in a housing U.S. Cl which contains the voltage arrest, The housing is tubular shaped, and a bias spring urges one of the contact blocks [58] Field Search "337/3 1 $2 together with the insulating member and the associated electrodes toward the other contact block. The other contact I 5 6] Rate" Cit d block is held in fixed position by a fusible material which when Mes e melted allows the entire assembly to slide within the housing. UNITED STATES PATENTS further electrode iS formed as a cylindrical member disposed within the housing and electrically coupled to one of Wanaselta the ontact blocks and having a urface positioned to and 2,371,314 1/1959 swam 61 161 spaced from the other contact block. When the fusible materi- 2,670,418 2/1954 xozcka r -337/161 al is melted, the other contact block is moved into engagement 2,481,298 9/ 1949 Eldndge "3337/31 with the surface of the further electrode. 2,934,625 4/1960 Patrichi ..337/239 3 Claims, 1 Drawing Figure BACKGROUND OF THE INVENTION 1. Description of the Prior Art- Over voltage arresters are generally known in the prior art, however such devices commonly have the problem of excessive heating which is harmful to the voltage arrester. For instance, voltage arresters may have a gas-type chamber which supports two oppositely poled electrodes which is normally gas tight. However, excessive heating of the electrodes could so deform the chamber that there is the danger of gas leakage into the vicinity of the electrodes. The present invention deals with an over voltage arrester which is adapted to greatly improve the heat dissipation from the electrodes and which has an improved fail-safe feature.

2. Field of the Invention The field of art to which this invention pertains is over voltage arresters and in particular to over voltage arresters having gastight chambers for the electrodes and having means for heat dissipation from the electrodes during operation thereof.

SUMMARY OF THE INVENTION It is a principal feature of the present invention to provide an improved over voltage arrester.

It is another feature of the present invention to provide an over voltage arrester which is capable of improved heat dissipation.

It is a principal object of the present invention to provide an over voltage arrester having a pair of electrodes disposed within a gastight chamber and having means for dissipating the heat from the electrodes to prevent overheating and a loosening of the gastight chamber.

It is another object of the invention to provide an over voltage arrester having a tubular insulating member and a pair of frustum-shaped electrodes disposed at opposite ends of the tubular insulating member to provide a gastight enclosure and having means contacting the frustum-shaped electrodes to conduct heat therefrom.

It is a further object of the present invention to provide an over voltage arrester as described above wherein relatively large contact blocks are caused to engage each of the frustumshaped electrodes and wherein the contact blocks are formed of a good thermally conductive material.

It is an additional object of the present invention to provide an over voltage arrester which is disposed in a tubular housing having an insulating member and frustum-shaped electrodes as described above with contact blocks disposed at opposite sides of the respective electrodes and having means biasing the entire assembly toward one end of the tubular housing.

It is also an object of the present invention to provide an over voltage arrester as described above wherein a further electrode in the form of a sleeve member is disposed in the tubular housing such that one end surface thereof is positioned adjacent to but spaced from one of the contact blocks whereby slidable movement of the contact block due to the biasing means causes the contact block to engage the further electrode as a fail-safe feature.

Another object of the present invention is to provide an over voltage arrester having the features described above wherein the slidable movement of the entire assembly within the tubular housing is prevented by the positioning of a fusible material within the tubular housing whereby excessive heat causes the fusible material to melt and allows the biasing means to move the entire assembly thereby allowing an electrical engagement between the associated contact block and the end of the further sleeve electrode thereby bypassing the over voltage arrester and providing a fail-safe feature.

BRIEF DESCRIPTION OF THE DRAWINGS The single drawing of the present invention shows an over voltage arrester in the form of a tubular insulating member having a pair of frustum shaped electrodes forming a cavity which is gas tight and having good thermal conducting contact blocks disposed at opposite sides of the voltage arrester. The entire assembly is disposed in a tubular housing and biasing means are provided as part of a fail-safe feature to move the entire assembly in response to excessive heat in a direction for electrically bypassing the voltage arrester.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention relates to an over voltage arrester which has improved features for heat dissipation and also has improved fail-safe features. While. over voltage arresters are well known in the art, it is common to have such devices over heat due to excessive arcing. Over heating tends to distort the electrode elements and may cause otherwise gastight chambers to leak.

The present invention provides an over voltage arrester in the form of a tubular insulating member which has a pair of electrodes disposed at the ends of the tubular member to form a closed chamber which is gas tight. The ends of the electrodes are sealed to the tubular member by a suitable means.

The electrodes are frustum-shaped members having surfaces disposed adjacent to each other and extending inwardly of the tubular insulating members. The device has relatively large contact blocks formed of a good thermal conducting material. The contact blocks make contact with the respective electrodes and carry away excessive heat which would otherwise be retained in the vicinity of the electrodes.

The contact blocks are slidably mounted in a tubularshaped housing. The slidable mounting feature is designed to provide a fail-safe character for the voltage arrester. In particular, therelatively large contact members and the voltage arrester are biased in one direction within the tubular housing. The biasing force is opposed by a slug or fusible material which when melted due to excessive heating of the contact members, allows the entire assembly to move under the biasing force. This movement then allows one of the contact blocks to make engagement with a further electrode which then bypasses the over voltage arrester.

In the preferred form of this invention, the contact blocks are solid metallic contact elements which are connected as the feed lines to the over voltage arrester. By using solid metallic contact blocks, these heat absorbing members can be firmly soldered to the frustum-shaped electrodes. These solid metallic contact blocks have a much greater heat capacity than the electrodes themselves and allow heat to be conducted away from the electrodes and especially away from the discharge chamber. The excessive heat, after being absorbed by the large contact blocks, is then dissipated to the surrounding area.

Referring to the drawings in greater detail, the single drawing in this application shows an over voltage arrester which is disposed in a housing 10. The housing 10 has an inner tubular surface 11 which supportsthe entire over voltage assembly and metallic contact blocks.

The over voltage arrester includes a ceramic insulator 12 which is shaped as a tubular member and a pair of electrodes 13 and 14. The electrodes l3'and 14 are frustum shaped and have flanges 15 and 16 which are secured by a suitable adhesive 17 to the tubular insulating member 12.

The frustum-shaped electrodes 13 and 14 have surfaces 18 and 19 which'are disposed adjacent to each other as shown. A conductive layer 20 is disposed within an opening 21 of the insulating member 12 and serves as an auxiliary ignition line which extends to the gastight space of the over voltage arrester.

Contact blocks 22 and 23 are provided at opposite sides of the voltage arrester and include large cylindrical portions 24 and 25 and smaller contact portions 26 and 27. The contact portions 26 and 27 engage the surfaces 28 and 29 of the frustum-shaped electrodes and conduct heat to the larger portions 24 and 25.

The contact block 22 is slidably disposed within the tubular surface 11 of the housing 10. However, a further electrode 30 is disposed in the form of a sleeve at the lower half of the tubular housing, and the contact block 23 is slidably disposed within the electrode or sleeve 30 as at numeral 31.

The electrode 30 has side walls 31 which surround the over voltage arrester and has a surface 32 which extends adjacent to but spaced from a surface 33 of the contact block 22. The electrode sleeve 30 has a lower surface 34 which engages an end face 35 of the tubular housing 10.

The contact block 23 is held spaced from the end of the electrode 30 at 36 by a soft solder pill 37. Essentially, the pill 37 is a fusible member which when over heated melts to allow the entire assembly to be free to move within the tubular hous- The spring biasing device 38 is disposed between the opposite end 39 of the housing and a surface 40 of the contact block 22. It can be seen, then, that the spring 38 biases the contact block 22 and the over voltage arrester, as well as the contact block 23 toward the fusible element 37. Therefore,

when the fusible element 37 melts due to excessive heating conditions, the entire assembly moves under the biasing force toward the end surface 36 of the sleeve 30. This movement causes the surface 33 of the contact block 22 to move into engagement with the end surface 32 of the sleeve 30 thereby bypassing the over voltage arrester and providing a fail-safe feature.

While it is indicated that ceramic may be used for the tubular insulating member 12, other suitable materials may also be utilized. The electrodes 13 and 14 may be formed of an alloy of nickel, iron and cobalt.

The contact blocks 22 and 23 are designed to be relatively massive with respect to the electrodes 13 and 14 and are firmly soldered thereto to provide good thermal conductivity from the respective electrodes.

As can be seen in the drawing, the space between the end 32 of the sleeve 30 and the end face 33 of the contact block 22 is less than the space between the surface 36 and an end face 41 of the contact block 23. This assures that the movement of the entire assembly will cause an engagement between the contact block 22 and the electrode 30.

In the operation of the device, an air gap 42 is normally provided between the end face 32 and the surface 33 of the contact block to provide an additional air spark gap which is in parallel to the over voltage arrester.

The over voltage arrester according to the present invention assures that the space available in the over voltage arrester is utilized to a maximum for metallic heat absorption and dissipation. The heat may be dissipated from the blocks 24 to the feed lines 43 and 44 respectively.

The frustum shape of the electrodes could also be entirely filled with a metallic contact block to further improve the heat elimination from the over voltage arrester.

We claim as our invention:

1. An over voltage arrcster comprising:

a tubular insulating member,

a pair of electrodes mounted in a gastight manner in said tubular member and each having an electrode surface spaced apart from a corresponding electrode surface of the other electrode,

relatively large and massive contact blocks formed of good thermal conducting material and being thermally coupled to respective ones of said electrodes for conducting away heat therefrom during operation of the voltage arrester,

said electrodes being frustum shaped and facing oppositely of each other, and

. means urging the electrodes inwardly of said tubular insulating member.

2. An over voltage arrester in accordance with claim 1 wherein said relatively large metallic contact blocks are firmly secured to said respective electrodes.

3. A voltage arrester comprising:

' a tubular insulating member having a pair of electrodes disposed therein and forming a gastight chamber therewith,

a tubular housing having first and second end surfaces, said tubular insulating member and associated electrodes being disposed insaid housing,

first and second relatively large contact blocks slidably disposed in said housing oppositely of said electrodes and contacting the same,

a heat sensitive member preventing the movement of said first contact blocks toward said first end of said tubular housing,

means biasing both said contact blocks and said tubular insulator and its electrodes toward said first end of said housing and a further electrode is provided in said housing and arranged to be engaged by said second contact block after said heat sensitive member has responded to an excessive heat condition and after said biasing means has moved said contact blocks,

insulating member and electrodes,

said biasing means comprising a spring member disposed between the second end of said tubular housing and said second contact block,

said further electrode comprising a sleeve positioned in said housing surrounding said insulating member and said associated electrodes, and

said sleeve abutting said first end of the housing and having a surface extending adjacent to and spaced from said second contact block. 

1. An over voltage arrester comprising: a tubular insulating member, a pair of electrodes mounted in a gastight manner in said tubular member and each having an electrode surface spaced apart from a corresponding electrode surface of the other electrode, relatively large and massive contact blocks formed of good thermal conducting material and being thermally coupled to respective ones of said electrodes for conducting away heat therefrom during operation of the voltage arrester, said electrodes being frustum shaped and facing oppositely of each other, and means urging the electrodes inwardly of said tubular insulating member.
 2. An over voltage arrester in accordance with claim 1 wherein said relatively large metallic contact blocks are firmly secured to said respective electrodes.
 3. A voltage arrester comprising: a tubular insulating member having a pair of electrodes disposed therein and forming a gastight chamber therewith, a tubular housing having first and second end surfaces, said tubular insulating member and associated electrodes being disposed in said housing, first and second relatively large contact blocks slidably disposed in said housing oppositely of said electrodes and contacting the same, a heat sensitive member preventing the movement of said first contact blocks toward said first end of said tubular housing, means biasing both said contact blocks and said tubular insulator and its electrodes toward said first end of said housing and a further electrode is provided in said housing and arranged to be engaged by said second contact block after said heat sensitive member has responded to an excessive heat condition and after said biasing means has moved said contact blocks, insulating member and electrodes, said biasing means comprising a spring member disposed between the second end of said tubular housing and said second contact block, said further electrode comprising a sleeve positioned in said housing surrounding said insulating member and said associated electrodes, and said sleeve abutting said first end of the housing and having a surface extending adjacent to and spaced from said second contact block. 